Inhibitory effect of rehmaionoside B, a constituent of rehmaniae radix, on isolated bladder and urethral smooth muscle of mice

We have investigated the effects of rehmaionoside B and other constituents of Rehmaniae radix on bladder and urethral smooth muscle strips of mice. Of the five constituents investigated, rehmaionoside B (1 mg/mL) most effectively inhibited the contraction induced by noradrenaline (10 μg/mL) in urethral smooth muscle. These constituents, especially rehmaionoside B, not only inhibited the spontaneous contraction but slightly relaxed the normal tone of the bladder smooth muscle. The relaxation induced by rehmaionoside B (0.1 mg/mL) corresponded to 26.4% of the isoproterenol (1 μg/mL) response. Rehmaionoside B also inhibited the PGF2α‐induced spontaneous contraction of the bladder. The treatment with rehmaionoside B significantly inhibited arachidonic acid‐induced contraction of the bladder. This response was similar to that induced by indomethacin. Rehmaionoside B inhibited both urethral and bladder smooth muscles, which may affect micturition. The effect of rehmaionoside B on the bladder was an indomethacin‐like action.